/*
 * Copyright (C) 2009 Yury Kudryashov.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package name.kudryashov.base;

import name.kudryashov.annotations.Immutable;

import java.util.NoSuchElementException;

/**
 * An {@link name.kudryashov.base.Option} representing no value.
 * @param <T> type
 */
@Immutable
final class None<T> extends Option<T> {

    private static final None NONE = new None();

    private None() {}

    public boolean isEmpty() {
        return true;
    }

    public T get() throws NoSuchElementException {
        throw new NoSuchElementException("None.get");
    }

    @SuppressWarnings({"unchecked"})
    public static <T> None<T> none() {
        return NONE;
    }

    @Override
    public String toString() {
        return "None";
    }

    private Object readResolve() {  return NONE; }

    private static final long serialVersionUID = -4559041553423105736L;
}